Comparison Of Shaping Ability With Different Instruments In Preparing Curved Root Canals

Objective:To compare the cutting ability,shaping ability and the influence on apical foramen among hand ProTaper,stainless steel K-files and rotary ProTaper files in preparing different curved root canal.Method:Forty simulated resin root canal blocks were randomly divided into four groups and prepared by hand ProTaper,stainless steel K-file and rotary ProTaper,respectively.Of them,12 blocks in group A,B,C consist of six 20°curved root canals(group A2,B2,C2)and six 30°curved root canals(group A3,B3,C3)each group.The curvature of the other 4 blocks in group D is less than 5°.Weighing the models and taking photos to the root canal orthotopically and apical foramen using digital camera before and after instrumentation.Finally,the transportation and stretched angle of root canal and the size of apical foramen were analyzed using special image software Auto-CAD.Result:(1)Group K-file has the best cutting ability than the other two groups(P＜0.05),the cutting ability of group rotary ProTaper is better than group hand ProTaper.At the same preparing condition,the loss in weight of 30°root canal is bigger than 20°root canal(P＜0.05),except group rotary Pro Taper.(2)The transportation of center in group K-file is the highest than that in groups Ni-Ti instrument(P＜0.05).In some portions of root canal,the transportation of center in group rotary ProTaper is higher than that in group hand ProTaper(P＜0.05). (3)The stretched angle of the root canal was increased according to the curvature of the root canal and group K-files is the highest than groups Ni-Ti files(P＜0.05).Rotary ProTaper is higher than that in group hand ProTaper,but no significance between them(P＞0.05).(4)The size of the apical foramen in group K-file is significantly bigger than the other groups after instrumentation(P＜0.05),and the size of the apical foramen of 30°root canal is bigger than 20°root canal.There was no significantly different between hand ProTaper and rotary ProTaper though the size of apical foramen in group rotary ProTaper is bigger than that in hand ProTaper at the same curvature and that in 30°root canal is bigger than in 20°root canal(P＞0.05)Conclusion:(1)The artherectomy ability of stainless steel K-file was higher than that of Ni-Ti instrument,the shape of the root canal was significantly changed after preparing using K-file.Thestretched angle of the root canal became large as the increase of root curvature,and the shape of apical foramen was destroyed seriously.(2)Hand ProTaper had the least artherectomy amount.It was better in keeping the shape of root canal and apical foramen than other groups,and was less influenced by root curvature.(3)The artherectomy amount of rotary ProTaper increased as the increase of root curvature.Rotary ProTaper had better shaping ability at apical region.The shape of apical foramen was better than K-file.But it caused excess artherectomy at middle root region.(4)Hand ProTaper was more stable and more suitable than rotary ProTaper for preparing midrange and severe curve root.